libstdc++: Reduce uses of std::numeric_limits

This avoids unnecessary instantiations of std::numeric_limits or
inclusion of <limits> when a more lightweight alternative would work.
Some uses can be replaced with __gnu_cxx::__int_traits and some can just
use size_t(-1) directly where SIZE_MAX is needed.

libstdc++-v3/ChangeLog:

	* include/bits/regex.h: Use __int_traits<int> instead of
	std::numeric_limits<int>.
	* include/bits/uniform_int_dist.h: Use __int_traits<T>::__max
	instead of std::numeric_limits<T>::max().
	* include/bits/hashtable_policy.h: Use size_t(-1) instead of
	std::numeric_limits<size_t>::max().
	* include/std/regex: Include <ext/numeric_traits.h>.
	* include/std/string_view: Use typedef for __int_traits<int>.
	* src/c++11/hashtable_c++0x.cc: Use size_t(-1) instead of
	std::numeric_limits<size_t>::max().
	* testsuite/std/ranges/iota/96042.cc: Include <limits>.
	* testsuite/std/ranges/iota/difference_type.cc: Likewise.
	* testsuite/std/ranges/subrange/96042.cc: Likewise.

libstdc++-v3/include/bits/hashtable_policy.h

@@ -32,8 +32,8 @@
 #define _HASHTABLE_POLICY_H 1
 
 #include <tuple>		// for std::tuple, std::forward_as_tuple
-#include <limits>		// for std::numeric_limits
 #include <bits/stl_algobase.h>	// for std::min, std::is_permutation.
+#include <ext/numeric_traits.h>	// for __gnu_cxx::__int_traits
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
@@ -506,14 +506,15 @@ namespace __detail
   inline std::size_t
   __clp2(std::size_t __n) noexcept
   {
+    using __gnu_cxx::__int_traits;
     // Equivalent to return __n ? std::bit_ceil(__n) : 0;
     if (__n < 2)
       return __n;
     const unsigned __lz = sizeof(size_t) > sizeof(long)
       ? __builtin_clzll(__n - 1ull)
       : __builtin_clzl(__n - 1ul);
     // Doing two shifts avoids undefined behaviour when __lz == 0.
-    return (size_t(1) << (numeric_limits<size_t>::digits - __lz - 1)) << 1;
+    return (size_t(1) << (__int_traits<size_t>::__digits - __lz - 1)) << 1;
   }
 
   /// Rehash policy providing power of 2 bucket numbers. Avoids modulo
@@ -556,7 +557,7 @@ namespace __detail
 	// Set next resize to the max value so that we never try to rehash again
 	// as we already reach the biggest possible bucket number.
 	// Note that it might result in max_load_factor not being respected.
-	_M_next_resize = numeric_limits<size_t>::max();
+	_M_next_resize = size_t(-1);
       else
 	_M_next_resize
 	  = __builtin_floorl(__res * (long double)_M_max_load_factor);

libstdc++-v3/include/bits/regex.h

@@ -973,11 +973,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 	  if (const size_t __n = std::min(_M_len, __s._M_len))
 	    if (int __ret = traits_type::compare(_M_data, __s._M_data, __n))
 	      return __ret;
+	  using __limits = __gnu_cxx::__int_traits<int>;
 	  const difference_type __diff = _M_len - __s._M_len;
-	  if (__diff > std::numeric_limits<int>::max())
-	    return std::numeric_limits<int>::max();
-	  if (__diff < std::numeric_limits<int>::min())
-	    return std::numeric_limits<int>::min();
+	  if (__diff > __limits::__max)
+	    return __limits::__max;
+	  if (__diff < __limits::__min)
+	    return __limits::__min;
 	  return static_cast<int>(__diff);
 	}
 

libstdc++-v3/include/bits/uniform_int_dist.h

@@ -32,7 +32,7 @@
 #define _GLIBCXX_BITS_UNIFORM_INT_DIST_H
 
 #include <type_traits>
-#include <limits>
+#include <ext/numeric_traits.h>
 #if __cplusplus > 201703L
 # include <concepts>
 #endif
@@ -88,7 +88,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 	explicit
 	param_type(_IntType __a,
-		   _IntType __b = numeric_limits<_IntType>::max())
+		   _IntType __b = __gnu_cxx::__int_traits<_IntType>::__max)
 	: _M_a(__a), _M_b(__b)
 	{
 	  __glibcxx_assert(_M_a <= _M_b);
@@ -126,7 +126,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        */
       explicit
       uniform_int_distribution(_IntType __a,
-			       _IntType __b = numeric_limits<_IntType>::max())
+			       _IntType __b
+				 = __gnu_cxx::__int_traits<_IntType>::__max)
       : _M_param(__a, __b)
       { }
 

libstdc++-v3/include/std/regex

@@ -53,6 +53,7 @@
 #include <cstring>
 
 #include <ext/aligned_buffer.h>
+#include <ext/numeric_traits.h>
 #include <bits/std_function.h>
 #include <bits/regex_constants.h>
 #include <bits/regex_error.h>

libstdc++-v3/include/std/string_view

@@ -459,11 +459,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       static constexpr int
       _S_compare(size_type __n1, size_type __n2) noexcept
       {
+	using __limits = __gnu_cxx::__int_traits<int>;
 	const difference_type __diff = __n1 - __n2;
-	if (__diff > __gnu_cxx::__int_traits<int>::__max)
-	  return __gnu_cxx::__int_traits<int>::__max;
-	if (__diff < __gnu_cxx::__int_traits<int>::__min)
-	  return __gnu_cxx::__int_traits<int>::__min;
+	if (__diff > __limits::__max)
+	  return __limits::__max;
+	if (__diff < __limits::__min)
+	  return __limits::__min;
 	return static_cast<int>(__diff);
       }
 

libstdc++-v3/src/c++11/hashtable_c++0x.cc

@@ -78,7 +78,7 @@ namespace __detail
       // Set next resize to the max value so that we never try to rehash again
       // as we already reach the biggest possible bucket number.
       // Note that it might result in max_load_factor not being respected.
-      _M_next_resize = numeric_limits<size_t>::max();
+      _M_next_resize = size_t(-1);
     else
       _M_next_resize =
 	__builtin_floorl(*__next_bkt * (long double)_M_max_load_factor);

libstdc++-v3/testsuite/std/ranges/iota/96042.cc

@@ -19,6 +19,7 @@
 // { dg-do compile { target c++2a } }
 
 #include <ranges>
+#include <limits>
 
 void
 test01()

libstdc++-v3/testsuite/std/ranges/iota/difference_type.cc

@@ -19,6 +19,7 @@
 // { dg-do run { target c++2a } }
 
 #include <ranges>
+#include <limits>
 #include <testsuite_hooks.h>
 
 void

libstdc++-v3/testsuite/std/ranges/subrange/96042.cc

@@ -19,6 +19,7 @@
 // { dg-do compile { target c++2a } }
 
 #include <ranges>
+#include <limits>
 
 constexpr bool
 test01()